Polyamide 66, structure

This polymerization is carried out in the two stages indicated above precisely because of the insolubility and infusibility of the final product. The first-stage polyamide, structure [IX], is prepared in polar solvents and at relatively low temperatures, say, 70°C or less. The intermediate is then introduced to the intended application-for example, a coating or lamination-then the second-stage cyclization is carried out at temperatures in the range 150-300°C. Note the formation of five-membered rings in the formation of the polyimide, structure [X], and also that the proportion of acid to amine groups is 2 1 for reaction (5.II). 

Polyamides are macromolecules with acidamide units —CONH—, where the chemical structure of the other parts of the monomers can be aliphatic and/or aromatic. Similar structures are found in nature, for example, polypeptides. Although in principle a large number of potential polyamide structures can be produced, only a few polyamides are produced in industrial scale. 

Figure 4.51(e) Displays the combined influences of polyamide structure and additives ... 

Ube developed the PA nanocomposite named Ecobesta to replace PVDF or other traditional barrier materials. The all-polyamide structure offers recycling advantages compared to traditional multi-materi designs. It incorporates ... 

Further variation is possible in the polymer structure and properties by using mixtures of the appropriate reactants such that the polymer chain can have different R and R groups. Thus polyamide structures of types XXXV and XXXVI are possible variations on structures XXXIII and XXXIV, respectively. A polymer such as XXXV or XXXVI has two different repeat units and is referred to as a copolymer the process by which it is synthesized is... 

I he properties of the simple amides are relevant to the chemistry of peptides and proteins, substances that are fundamental to all life as we know it. Indeed, the characteristics of peptides and proteins are primarily due to their polyamide structures. For this reason, it is important to know and understand the chemistry of simple amides. 

The number 6 specifies the number of carbons in each monomer unit comprising the polyamide structure. By this code, nylon-6,6 is (—NH(CH2)6NHCO(CH2)4 CO—-),. 

Amino acids are the building blocks of the polyamide structures of peptides and proteins. Each amino acid is linked to another by an amide (or peptide) bond formed between the NH2 group of one and the C02H group of the other ... 

Several important drugs are peptidomimetics, which were discovered among substances isolated from natural sources. Many of these exhibit complex structures, so that their total synthesis is a challenge. A few examples of such materials will be considered in this section. The term peptidomimetic is subject to more than one definition here, peptidomimetics are considered as those substances which contain amide or amide-like bonds in the main chain, but do not otherwise differ markedly from the prototypical peptide polyamide structure. Others define the term much more broadly, in which case many other substances would have to be considered. 

Nylon Resins. Nylon engineering thermoplastic resins have the following polyamide structures ... 

The products (5) were isolated as the hexafluorophosphates. IR and NMR data confirmed the linear polyamide structures. However, viscometric and vapor pressure osmometric investigations on the polymers were found to be inconclusive because of polydissociation in solvents. 

If the polymer molecule is stiff, it will have less tendency tocoil upon itself, and most segments of a given molecule will contact segments of other macromolecules. A prime example is the aromatic polyamide structure ... 

Figure 1.9 Various polyamide structures derived from sugars [16].

The combination of piperazine with trimesoyl chloride in composite membrane form was named NS-300. Trimesoyl chloride leads to a crosslinked polyamide structure. Apparently, however, considerable formation of hydrolyzed carboxylate groups also occurs. This is evidenced by the anion selectivity of the membrane, demonstrated by the sequential salt rejection data in Table 5.4 for a series of salts on test with a single set of membrane specimens. 

TRADE NAMES Nomex, Teijinconex, Fenilin CLASS Aromatic polyamides STRUCTURE Q O... 

The connection between the altered basic molecular chain and macroscopic properties is explained using the example of a polyamide structure. Polyamides are nitrogenous thermoplastics the base units of which (CH2) are interlinked by carboxylic acid amide groups (short form amide groups). 

For example, if the time for the process to occur is faster than the longest relaxation time, then the fluid behaves more like an elastic solid. For the liquid crystalline systems there seems to be two relaxation times which are important. One is the time for relaxation of orientation and the other is the time for relaxation of stress. Whereas these phenomena are connected for flexible chain polymers, they seem to separate for liquid crystalline polymers. In other words, there are several stress free states for LCP. Some of the behavior observed may be partly due to the copolymer nature of thermotropic systems. However, the lyotropic systems based on the polyamide structure also exhibit similar behavior. 

Key words vegetable oil-based addition polymers and polyamides, preparation of addition polymers and polyamides, structure-property relationships of addition polymers and polyamides, application of addition polymers and polyamides. 

The yield of crosslinking correlates well with the number of methylene groups (-CH2-) present in the polyamide structure. Absorbed water in the polyamide enhances cross-linking at higher concentration, and inhibits the process at low concentration. The presence of water does not appear to significantly affect the scission process. 

Step growth polymers are governed by the same rules. In many of these polymers, chains are less regular, but more polar. Two polymer structures which lead to such high crystallinity that the polymers have been used for fibres are the polyamide structure of Nylon , and the polyester structure of Terylene . The latter is a polymer derived from /erephthalic acid and Qi iylene glycol from which the name derives. Bulk nylon is a waxy solid of such toughness that a major use is in gear wheels in small machinery. 

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